Rules and Guidelines
Want to participate in the discussions? Please read our Community Rules and Guidelines. Need some help? Visit Support and Answers.

  • State Not Answered
  • Locked Locked
  • Replies 18 replies
  • Subscribers 32 subscribers
  • Views 2412 views
  • Users 0 members are here
Options
You may also be interested in
This discussion has been locked.
You can no longer post new replies to this discussion. If you have a question you can start a new discussion

MCCBs

richard64
Ok, no showers on this one.

Where can I find max zs and time current characteristics for mccbs.

There's nothing in the BBB covering them (as far as I can see).

Thank you.
Parents
  • Former Community Member
    0 Former Community Member

    mapj1:

    BTW it was OMS who brought up the concept of only considering the more 'credible faults ' though I agree entirely with the sentiment - incredible faults may bulk up the Risk Assessment, if you are paid by weight of paper, but measures to avoid them are largely nugatory but can be comical.





     



     

    OK - for clarity, I wasn't suggesting that we don't design for all of the faults that may occur within a system (electrical protection from O/L, SC and E/F should be achieved throughout) - just that were a fault to occur at a particularly unusual position, then we might not achieve discrimination - ie we would say we would have partial co-ordination. So an example might be someone driving a silver stake through a cable about 2m downstream from the panel - which in reality means someone has climbed up to reach the cable tray/ladder and given the cable a bloody good insult - at that point I wouldn't worry unnecessarily that the feeder breaker and the main panel device have raced each other to the final and both operated, leaving some healthy circuits off - in most cases, it would be so rare that it would be tolerable - and if it ain't then it needs more money spending to absolutely ensure full discrimination at any point in the system (so add £XX thousands for things like bus bar protection zones, line differential protection on feeders, fail to trip schemes, restricted earth fault protection zones, circuit breaker restraint schemes (with the consequent increase in switchboard fault rating (eg increase from 1 to 3 second protection)) etc etc


    Regards


    OMS

Reply
  • Former Community Member
    0 Former Community Member

    mapj1:

    BTW it was OMS who brought up the concept of only considering the more 'credible faults ' though I agree entirely with the sentiment - incredible faults may bulk up the Risk Assessment, if you are paid by weight of paper, but measures to avoid them are largely nugatory but can be comical.





     



     

    OK - for clarity, I wasn't suggesting that we don't design for all of the faults that may occur within a system (electrical protection from O/L, SC and E/F should be achieved throughout) - just that were a fault to occur at a particularly unusual position, then we might not achieve discrimination - ie we would say we would have partial co-ordination. So an example might be someone driving a silver stake through a cable about 2m downstream from the panel - which in reality means someone has climbed up to reach the cable tray/ladder and given the cable a bloody good insult - at that point I wouldn't worry unnecessarily that the feeder breaker and the main panel device have raced each other to the final and both operated, leaving some healthy circuits off - in most cases, it would be so rare that it would be tolerable - and if it ain't then it needs more money spending to absolutely ensure full discrimination at any point in the system (so add £XX thousands for things like bus bar protection zones, line differential protection on feeders, fail to trip schemes, restricted earth fault protection zones, circuit breaker restraint schemes (with the consequent increase in switchboard fault rating (eg increase from 1 to 3 second protection)) etc etc


    Regards


    OMS

Children
No Data

Community Rules & Guidelines